1. Field of the Invention
The invention relates to a catheter system and method for combined injection of a liquid embolic composition and an embolic solidification agent, and more particularly, to a catheter system including a multiple lumen catheter for injection of a liquid embolic composition through a first lumen and an embolic solidification agent through a second lumen. The catheter system is used for delivery of the embolic composition in a controlled manner for embolizing blood vessels.
2. State of the Art
In many clinical situations it is desirable to selectively occlude blood vessels for a variety of purposes, such as, the control or prevention of bleeding, the prevention of blood supply to tumors, and the blocking of blood flow within an aneurysm. Embolization of blood vessels has been performed by employing certain polymer compositions and/or particulate including silicone balloons, metallic coils, PA particles, gelatin, sclerosing material, and the like, to selectively block blood flow in the blood vessels.
Intracranial aneurysms are present in between one and nine percent of the population and rupture at a rate of more than 50,000 per year in North America. Intracranial aneurysms are abnormal blood filled dilations of a blood vessel wall which may rupture causing significant bleeding and damage to surrounding brain tissue or death. Traditionally, intracranial aneurysms have been surgically clipped to reduce the risk of rupture by placing a metal clip around the neck of the aneurysm to cut off and prevent further blood flow to the aneurysm. However, many aneurysms cannot be treated surgically because of either the location and configuration of the aneurysm or because the condition of the patient does not permit cranial surgery.
When aneurysms cannot be treated surgically or when surgery is considered to be too risky or invasive, aneurysms may be treated endovascularly with coils. The coils are placed in the aneurysm by extending a catheter endovascularly to the site of the aneurysm and passing single or often multiple platinum or tungsten coils through the catheter into the aneurysm. The coils placed within the aneurysm create a thrombus which occludes the aneurysm and prevents further blood flow to the aneurysm. The treatment of intracranial aneurysms with coils isolates the aneurysm from arterial circulation helping to guard against rupture and further growth of the aneurysm. However, the use of platinum coils to treat intracranial aneurysms may not be a permanent solution because the blood clot around the coils may declot or dissolve due to the dynamic nature of the blood clotting function. Once a clot formed around the coils in an aneurysm declots, the coil can no longer perform its function of occluding the aneurysm. In addition, the coils may become dislodged and enter the patient's blood stream causing blockages at other locations within the vascular system.
Another drawback associated with the use of coils to occlude an aneurysm is that the coils are known to compact over time leaving cavities for subsequent aneurysm growth. In addition, if a subsequent surgical clipping procedure is warranted, it can be difficult to place the clip over the coil mass.
Aneurysms having large necks are not easily treated by either surgical clipping or by coils because the aneurysm neck may have a shape which cannot be completely clipped surgically and the coils may tend to become dislodged from the aneurysm when the neck is particularly large.
One minimally invasive procedure for treating intracranial aneurysms which addresses the problems with the surgical clipping and coil techniques involves the endovascular injection of a liquid embolic composition which solidifies in the aneurysm to occlude the aneurysm. The liquid embolic composition generally includes a water-insoluble, biocompatible polymer and a biocompatible solvent. Once the liquid embolic composition is injected into the aneurysm, the biocompatible solvent dissipates into the blood and the polymer solidifies to occlude the blood flow through the aneurysm.
Typically, liquid embolic compositions include a water insoluble, biocompatible, non-biodegradable polymer dissolved in a biocompatible solvent and preferably these compositions include a radiopaque material which allows the physician to view the embolization procedure by fluoroscopy. Prior to delivery of the embolic composition to the aneurysm, the aneurysm and delivery device are preferably positioned so that the liquid embolic composition will be delivered by gravity into the aneurysm and will remain in the aneurysm (with the aneurysm neck pointing up). As the embolic composition is delivered to the aneurysm, the solvent dissipates from the polymer material causing the polymer material within the aneurysm to solidify.
Depending on the rate at which the liquid embolic material is injected into the blood vessel and the amount of blood flow present, the polymer may remain in liquid form for a period of time while the solvent dissipates into the blood stream. Moreover, the solvent may not be completely dissipated from a center of the polymer mass creating a mass with a solid outer shell and liquid interior. In addition, the solvent concentration at the point of injection may increase to a point where small strings of unsolidified polymer material may separate from the polymer mass and be carried away in the blood stream where it can occlude an undesired vascular location. Since the solvent generally has a density greater than water or blood, gravity may hold the solvent in the aneurysm and prevent the polymer from solidifying.
Accordingly, it would be desirable to provide a method for controlling the solidification of the polymer material during injection. It would also be desirable to provide a method for filling an aneurysm which is not positioned such that gravity may be used to cause the embolic composition to flow into and remain in the aneurysm, since a patient's anatomical position cannot always be in a gravity dependent position.
As disclosed in U.S. patent application Ser. No. 08/730,701, embolization of a blood vessel with a liquid embolic composition generally includes a preparatory step of flushing a delivery catheter through which the liquid embolic composition is to be delivered with the biocompatible solvent material to remove any aqueous material from the catheter. The removal of any aqueous material from the catheter inhibits solidification of the embolic composition within the catheter during delivery. This preliminary step of flushing with the solvent must be done at a slow flow rate to prevent damage to the blood vessel caused by high concentrations of the solvent which can be toxic and may cause vascular spasms. However, it would be desirable to be able to perform the preliminary flushing of the delivery catheter without concern of causing tissue damage.